Caleb MorganBy Caleb Morgan

Updated November 2026

A bike tire size chart translates the numbers printed on a tire sidewall into a size that actually fits your wheel. Once you know how to read those markings, you can confirm whether a replacement tire will mount on your rim, how wide it will run, and how much air it needs. This guide walks you through the common size systems and shows you how to match them safely.

Understand the Three Common Size Systems

Most bike tires are labeled in one of three ways, and many sidewalls show more than one. The label you see depends on the bike type and the region where the tire was designed.

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  • ETRTO (European Tyre and Rim Technical Organisation): A two-number format such as 28-622 or 32-584. The first number is the tire width in millimeters. The second is the bead seat diameter in millimeters, which must match your rim.
  • Inch sizing: Labels such as 26 x 2.1 or 700 x 25c. These are common on mountain, hybrid and road bikes, though the same wheel can carry different inch labels depending on the manufacturer.
  • Metric sizing: Labels such as 700 x 28C, where 700 refers to the approximate outer diameter in millimeters and 28 is the tire width.

How to Match a Tire to Your Wheel

Start by reading the size printed on your current tire or on the rim sidewall. Then compare it to the chart below. Matching the bead seat diameter is the most important step, because a tire with the wrong bead diameter will not seat properly, even if the width looks close.

Common label ETRTO equivalent Typical bike type
26 x 1.95 50-559 Older mountain and cruiser bikes
27.5 x 2.25 57-584 Mountain bikes (650b)
29 x 2.2 55-622 Mountain bikes
700 x 25c 25-622 Road and gravel bikes
700 x 32c 32-622 Hybrid and gravel bikes

Two tires share a label when they share a bead diameter. A 700c tire and a 29-inch mountain tire, for example, use different bead diameters and cannot be swapped. Check the ETRTO number whenever you are unsure, since it is the most precise measurement.

Check Width, Pressure and Clearance

Once the bead diameter matches, confirm that the tire width works with your rim and frame. Rim manufacturers usually list an acceptable tire width range, and frames specify maximum tire clearance. Manufacturers generally advise against exceeding these limits.

  1. Measure the internal width of your rim, or look up the rim specification.
  2. Confirm the tire width falls inside the rim’s recommended range.
  3. Check the maximum tire width the frame or fork allows.
  4. Note the pressure range printed on the new tire and make sure your pump can reach it.

Common Mistakes

  • Choosing by width alone and ignoring the bead diameter.
  • Assuming “26 inch” always means the same wheel. Older 26-inch bikes often use different standards.
  • Fitting a very wide tire to a narrow rim, which can cause poor handling and a higher risk of pinch flats.
  • Ignoring the maximum pressure on the sidewall and overinflating.

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A floor pump with a pressure gauge lets you reach the exact pressure printed on the sidewall. View on Amazon

FAQ

Can I use a different tire size than the one on my bike?

Only if the bead diameter matches your rim and the new width fits inside the rim and frame limits. A tire with the wrong bead diameter will not seat safely.

What does the first number in an ETRTO size mean?

It is the tire width in millimeters. The second number is the bead seat diameter, which must match your rim.

Where can I find the size of my current tire?

Look at the sidewall, where the size is usually printed in both inch and ETRTO formats. If it is worn off, measure the rim and check the bike manufacturer’s specifications.

Conclusion

A bike tire size chart is most useful when you match the bead diameter first and the width second. Read the ETRTO number whenever you can, since it removes the confusion between inch and metric labels. If you are still unsure about compatibility, a local bike shop can confirm the fit before you buy.

Ready to choose one?

Caleb Morgan

About Caleb Morgan

Caleb Morgan is part of our editorial team and reviews and edits our cycling for beginners guides, checking product details against manufacturer specifications and owner feedback.